Apparatus for regulating propulsion power plants



APPARATUS FOR REGULATING PROPULSION POWER PLANTS Filed Sept. 14. 1946 July 14, 1953 H. M. OGLE ETAL 2 Sheets-Sheet 1 rw m erw '8 w fim w t E ,t M A t m w A vwxan .mH u .m 0? e a naph M T w Qm q R July 14, 1953 H. M. 061.12 El'AL APPARATUS FOR REGULATING PROPULSION POWER PLANTS Filed Sept. 14, 1946 2- Sheets-Shgaet 2 5 d mwam w tMB m w A mw ww r .l Dwpm M T Patented July 14, 1953 APPARATUS FOR REGULATIN G PROPUL- SION POWER PLANTS Hugh M. Ogle and Donald E. Garr, Schenectady, and Martin A. Edwards, Scotia, N. Y., assignors to General Electric Company, a corporation of New York Application September 14, 1946, Serial No. 697,058

Claims.

This invention relates to regulating means for prime mover powerplants, particularly to those jet reaction of the hot gases exhausted from the powerplant through a suitable nozzle. Powerplants of this type are disclosed in applications Serial No. 525,391, filed March 7, 1944' in the name of Dale D. Streid, Patent 2,432,359, and Serial No. 541,565, filed June 22, 1944 in the name of Alan Howard. It is also possible to arrange the powerplant to drive a variable pitch propeller, the major portion of the'useful output of the powerplant being delivered to the propeller through suitable gearing, while'la smaller portion produces useful thrust by the jet reaction of the gases exhausted from the powerplant through a propulsion nozzle directed rearwardly. An aircraft gas turbine of this type is disclosed in application Serial No. 506,930, filed October 20, 1943, in the name of Alan Howard now U. *8. Patent No. 2,479,573 of August 23, 1949.

Our prior application Serial No; 605,960, filed July 19, 1945, now U. S. Patent No. 2,622,393 of December 12, 1952 disclosed a regulating system particularly adapted for pure jet propulsion powerplants of the type described in the abovementioned Streid Patent No. 2,432,359. The present invention has some features in common, but is particularly adapted to the control of a powerplant of the type described in the above-mentioned Howard Patent No. 2,479,573, in which the gas turbine drivesa suitable variable pitch propeller.

The general object of the invention isto provide an improved method and apparatus for controlling a prime mover powerplantfor driving an adjustable torque load device, such as an adjustable pitch propeller for propulsion of a body in' a fluid medium.

A specific object is to provide a regulating system for a powerplant of the type described which controls the supply of operating medium to maintain the rotational speed constant and varies the load output by adjusting the torque input to the load device, means being provided for the direct manual control of the operating medium supply during the starting cycle.

A further object is to provide regulating apparatus of the type described which is adapted for efiectively controlling turbine powerplants having rotors of large rotational inertia.

Still another object is to provide a high temperature turbine powerplant regulator including automatic safety devices for preventing excessive temperatures.

Another object is to provide an improved regulator of the type described for an aircraft gas turbine powerplant driving an adjustable pitch propeller in which the torque control means and the motivefiuid control means are automatically recalibrated in accordance with changes in altitude and certain other operating conditions of the powerplant.

Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a diagrammatic representation of an aircraft gas turbine powerplant arranged to be controlled by a regulating system in accordance with our invention; and Fig. 2 is a schematic representation of :a regulator for effecting our improved method of control.

Since the advent of the gas turbine propulsion powerplant for aircraft, many studies have been made to determine the best method of utilizing the output of the powerplant in order to secure the best over-all propulsive efiiciency. The consensus of opinion resulting from thesestudies has been that for aircraft speeds below 600 miles per hour :a variable pitch propeller receiving the major portion of the useful output of the powerplant promises the best efiiciency.

Introducing the variable pitch geared propeller into the propulsion system carries with it many new'problems. Existing variable pitch air-screws and the means for controlling them, designed for use with reciprocating internal combustion engines, have been found to be not directly applicable to use in connection with turbine prime movers. When a variable pitch propeller is used with a conventional reciprocating engine, the rotational inertia of the propeller itself is much greater than that of the moving parts of the reciprocating engine. Therefore, the speed of the reciprocating engine can be readily and quickly controlled'by varying the pitch of the propeller, a small change in pitch having an immediate effect on the engine speed. On the other hand, the rotational inertia of the gas turbine rotor and parts connected to it is many'times that of the propeller. Therefore, a change in propeller pitch affects the rotational speed of the powerplant only after an appreciable time lag. For this reason, it is not readily feasible to control powerplant speed by adjusting the propeller pitch and relying upon changes in propeller shaft torque to produce a speed change in the desired direction.

It may'also be noted that a reciprocating internal combustion engine is capable of operating over a wide range of speeds without adversely affecting the engine, both the full load and cruising speeds being a fraction of'the maximum permissible speed which the engine structure will stand. On the other hand, witha gas turbine powerplant the efliciency and fuel economy increase progressively with an increase in speed so that it is desirable to operate the powerplant at a constant speed which is as close as possible to the maximum safe operating speed. With the speed maintained constant, the load may be varied from the cruising or maximum economy value to the full load or maximum output value by regulating the fuel supply to vary the tem= perature level at which the powerplant operates. Because of the high temperatures at which the turbine rotor and other components operate, in combination with the fact that the normal speed is established as close as possible to the maximum permissible speed, transient over-speed conditions must be very carefully prevented; since even a temporary over-speed of a few per cent may result in the destruction of the engine and perhaps the aircraft. When used in high altitude aircraft, it is of course necessary that the powerplant operate over an extremely wide range of atmospheric conditions and loads. With the many complex factors which must be taken into consideration, and in view of the enormous forces to be controlled, a satisfactory regulating system must be capable of effecting its functions very precisely and with the utmost reliability.

The present invention provides a new method and apparatus for controlling a propeller prov pulsion powerplant of the type described which appears to meet adequately the exacting requirements outlined above.

In contrast to previously known regulating systems for prime movers driving automatic adjustable pitch propellers, our invention comprises means for holding the powerplant speed constant and causing the propeller pitch control means to vary the pitch of the blades so as to maintain the propeller shaft torque constant at a value corresponding to the desired horsepower output. To this end our regulator includes a centrifugal speed responsive governor arranged to vary the fuel input to the powerplant so as to limit the rotational speed. A device responsive to;the propeller shaft torque trans .its a signal to the regulator which in turn actuates the propeller pitch control in such a manner as to maintain the shafttorque constant. As in the regulator described in our previousapplication referred to above, means are provided for recalibrating the regulator in accordance with ambient atmospheric conditions so that for'all altitudes and in let conditions the full load position of the operators throttle will produce the maximum perload setting. Means are also provided for preventing excessive rotational speed of the powerplant, as well as'operation at excessive temperature levels. Special means are provided for retion.

4 calibrating the regulator so as to call for less propeller shaft torque in the event operating conditions are such that the output called for by the operator cannot be safely attained Without producing an excessive temperature level. Suitable manual control means are .provided, with linkages connecting the various components of the regulating system so arranged that during starting the fuel pressure is controlled manually; then when the speed rises to a preselected value, the speed responsive governor comes into control; and after substantially full rated speed is attained, the load is varied by changing the propeller pitch to vary the shaft torque.

Referring now to Fig. 1, our control system is represented as applied to an aircraft gas turbine of thetype described in the above-mentioned application of Alan Howard, Serial No. 506,930, new Patent No. 2,479,573. ihe powerplant comprises an axial flow compressor I mounted on a common shaft with a single-stage axial flow turbine rotor 2, a plurality of combustion chambers or combusters 3, circumferentially spaced around the casing of compressor 1 with their discharge ends arranged to deliver hot motive fluid through suitable nozzles 4 to the buckets of the turbine rotor 2. Air enters the compressor I through an annular air inlet grill 5. From the discharge of compressor I, air is distributed to the respective combustors 3 in a manner more clearly disclosed in the abovementioned Howard Patent No. 2,479,573.

Each coinbustor contains a nozzle 6 which introduces fuel into the combustion space in a suitable manner, and certain of the combustors contain a suitable ignition device (not shown). The nozzles represented diagrammatically in Fig. 1 may advantageously be of the type known as a duplex fuel nozzle, more specifically described in an application Serial No. 622,604, filed October 16, 1945, in the names of Charles D. Fulton and David C. Ipsen now U. S. Patent No. 2,590,854 of April 1, 1952. The details of the fuel nozzle system are not material to an understanding of the present invention; but it maybe noted that the duplex nozzle is especially designed to produce a satisfactory fuel spray over the extremely wide range of operating conditions encountered by aircraft gas turbine powerplants. This nozzle equires two separate'supply passages, represented by the two annular headers 1 and 8 provided with branch conduits 9 and [0, respectively, to each of the nozzles 65. Fuel is supplied by a pump described hereinafter through a supply conduit H and a flow divider [2, a special type of metering valve arranged to deliver fuel at two different pressures to the headers 'l and 8, as described more specifically in the abovementioned application of Fulton and Ipsen.

While Fig. 1 illustrates a fuel spray system incorporating a duplex type spray nozzle and flow dividenit is to be understood that the precise type of nozzle system to which the conduit I I delivers fuel is immaterial to the present inven- Other types of fuel and fuel introducing systems may be used, provided they have the required range and other characteristics'necessary to successful operation in air-craft powerplants.

Thehot gases discharged from turbine 2 flow through an annular passage i5 defined between the tailcone It and inner conical housing It. A suitable exhaust conduit is may be connected by a flanged joint at Ii to tail-cone l3, and serves to conduct the exhaust gases to an outlet (not shown) which may preferabl define a nozzle designed to produce jet thrust.

The forward end of the turbine-compressor rotor is provided with a shaft extension l8 carrying a driving pinion l9. This gear eshe with a plurality of planet pinions 20 carried by a spider member 2| secured to a propeller drive shaft 22 supported in a suitable bearing 23.

Shaft 22 is arranged to drive both the variable pitch propeller 24 as well as a plurality of accessory devices supported on and driven from gearing. within the accessory drive casing 5. These accessories may include an electric starter motor 26, a pressure oil pump 21, a fuel oil pump 28, and a regulator 23 arranged in accordance with our invention. A number of other accessories (not shown in Fig. 1) may be driven from the accessory drive casing 25, for instance an electric generator, tachometer generator, hydraulic power pump, 6130.. V

The spinner housing 36 of propeller 24 contains the mechanism for adjusting the pitch of blades 3|, which mechanism is under the control of a pitch adjusting lever 32. This blade adjusting mechanism 32 may be of any suitable type, the precise details thereof being unnecessary to an understanding of the present invention. It may be noted, however, that each position of lever 32- corresponds to a predetermined pitch or angle of attack of the propeller flcient to provide the force needed to balance the reaction on ring gear 20a produced by the f a planetary gearing. Conversely if the torque shaft 22.

gearing I9, are a plurality of hydraulic cyl-' inders 33, each connected to and arranged to resist rotation of the stationary ring gear 20a with which the plane pinions 20 mesh. One of these hydraulic cylinders is a master cylinder, shown rotated somewhat out of the plane of the planetary gearing and to an enlarged scale at 34. This master cylinder includes a housing 35 defining a cylindrical bore in which is slidably arranged a piston 36, the piston 36 and cylinder 35 defining a pressure chamber 31. One or more ports 38 in piston 36 communicate With the pressure chamber 31 and have an opposite end portion arranged to come into alignment with a drain port 39 in cylinder 35 when the piston 36 moves to the right. Piston 36 is connected by means of a link 4| to an abutment 40 fixed to ring gear 20a.

The operation of the torque-sensing master cylinder 34 is as follows. It will be understood that the ring gear 20a of the planetary reduction gear train is arranged to float on suitable bearings (not shown), the reaction Produced by the planetary gears being balanced by a force on the ring gear produced by hydraulic pressure in the cylinders 33, 34., This is a diagrammatic representation of a well-known arrangement for measuring the torque transmitted by a planetary reduction gear train, and more specific details are believed unnecessary to an understanding of our invention.

If the torque transmitted by the gearing to propeller shaft 22 should decrease, then the hydraulic pressure in chamber 31 will cause piston 36 to move to the right so as to align the ports 39 with passages 38 and permit some of the liquid in the cylinder to drain off, until the pressure in chamber 3'! falls to a value just sufshould increase, then piston 36 would move to the left closing off drain ports 39 until the oil pressure again builds up in chamber 31 so that the force produced on piston 36 balances the increased torque. Thus, it will'be seen that the hydraulic pressure in chamber 31 may be taken as a measure of the torque transmitted from the turbine-compressor shaft I8 to the propeller Supported on tail-cone I3 is a temperature responsive device 42. The details of this thermal device are described more in detail in our p viously filed application Serial No. 605,960 now Patent No. 2,622,393. t may be stated. briefly that the device consists of an outer tube 43 made of a suitable temperature resisting metal and an inner rod 44 made of a non-expanding material such as quartz. The Quartz rod 44 extends into a housing 45 through a bellows seal and engages a cantilever spring 46. of the spring engages the end of an adjusting screw 41, while the other end engages a slidable plunger 48 supported by housing 46 in cooperative relation with an oil bleed port 49. Oil entering housing 45 through the port 49 is drained therefrom through a port 50 and a suitable drain conduit. While only one thermal device 42 is shown, it will be understood by those skilled in the art that two or more similar devices, connected in parallel and spaced around thecircumference of tail-cone [3, may be used to obtain an' average indication of the temperature of the turbine discharge gases.

The fuel pump 28 may be of any suitable type having a variable displacement which is Varied in accordance with a signal supplied to an automatic control device incorporated in the pump. The pump andits integral displacement control device may advantageously be of the type represented in our previous application Serial No. 605,960 now Patent No. 2,622,393. The precise mechanical details of the pump used are not material to an understanding of the present invention; it is necessary only to observe that pump 28 delivers fuel to conduit II at a variable pressure in accordance with a control signal, such as a hydraulic pressure supplied to it through conduit 63.

The pressure oil pump 2'! constitutes a separate source of oil for actuating the torque measuring system. Pump 2! may be of any suitable positive displacement type, and is geared directly at a fixed ratio'to the propeller shaft 22 by means ofthe gearing contained in the accessory drive casing 25.

The regulator. 23 will be described more particularly in connection with Fig. 2, but it may he noted here that it is provided with a single manually controlled shaft '5! arranged to be positioned by means of a lever 52 connected by means of alink 53 to a throttle lever 54, which is shown in Fig. l in its off position.

Lever 52 is also connected by means of a link One end stopcock to conduit I I which supplies the fuel charge pressure of fuel pump 28 is automatically varied in accordance with a control oil pressure communicated to it from regulator 29 through conduit 63.

The pressure oil pump 21 receives oil from a storage sump or tank (not shown) and delivers it to the hydraulic torque cylinders 33, 34 through conduit Glp Branching off from conduit BI is a conduit 62 which communicates the pressure in the torque-sensing chamber 3! to the regulator 29. v V

The static pressure at the inlet 5 of compressor I is communicated to the regulator 29 by a conduit 64 and the compressor discharge pressure is communicated from the outlet of the com-' pressor I to regulator 29 through conduit 65; The thermal element 42 is connected to regulator 29 by means of a supply conduit 66 and a return pipe 51. A propeller pitch control shaft 68b projecting from the housing of regulator 29 is connected by suitable means, for instance a lever 68 and link 32a, to actuate the pitch control lever 32.

Regulator peller pitch control motor I4, a compensating motor I2, and a manual control shaft 5i which carries a number of cams, one for controlling the fuel pressure directly, one for adjusting the torque control means, and another for adjusting the speed governor.

Because of the absolute reliability required of such a regulator, it is necessary to take special precautions so that friction in the various hydraulic motors and pilot valves will not introduce disturbing forces into the system. To this end, the various slidable elements are arranged so that they, or the bushings in which they slide, can be rotated by suitable gearing connected to the regulator drive shaft 80. It will be seen from Fig, 2 that gear 8| on shaft 89 is arranged to drive gear 82, while a second gear 83 on shaft 80 drives gear 84. Mounted on the shaftof gear 84 is a second gear 85 arranged to drive gears 85 and 37. Gear 83 is arranged to rotate with gear 8? and in turn drives gears 89, 90, BI, 92, and 33. It will be observed that gear BI is comparatively wide with respect to gear E22, so that the latter can reciprocate vertically and still remain'in engagement with gear BI. Likewise gears 92 and 93 are made sufiiciently wide so that they can reciprocate while remaining in driving engagement with gear 9i.

It should be noted that the schematic layout shown in Fig. 2 represents a "developed view of the apparatus. In building an actual regulator,

this developed layout would be rolled up so that all the components shown are arranged compactly within a cylindrical space, the various elements being so located relative to each other that the gear 82 will mesh directly with gear 8|, gear 83 with gear 35, 81 with 8, 88 with 89, and QI with 93. With this arrangement, all of the reciprocating elements subject to friction forces which might produce erratic action of the governor are provided with continuous relative rotational movement so that static friction effects are eliminated.

The construction and arrangement of the various components of the regulator 29 will now be described in more detail.

Fuel pressure control pump 69 may be of any suitable type, although a 7 simple gear type has been shown in the drawing.

The pump 69 delivers oil into a main header IOI which is provided with a pressure relief valve I02 arranged to maintain substantially constant the pressure in the header.

The primary control of the fuel pressure delivered by pump 28 is effected by means of the fuel pressure control motor I0, which consists of a piston IE3 slidably arranged in a cylinder so as to define a control oil pressure chamber I04. Chamber I04 communicates by way of conduit I05 with the automatic pressure responsive control device incorporated in fuel pump 28. As indicated above, the automatic variable displacement pump 28 is so arranged that an increase in the control pressure supplied through conduit I05 results in a proportional increase in the pressure of the fuel supplied to conduit II and the spray nozzle system.

The control oil pressure in chamber I04 is 7 established by means of a fuel pressure control is provided with a portion of reduced diameter- II2 defining an annular passage with the bore I I Ii. The lower end of pilot I06 forms a cylinder 7 which closes off the ports communicating with groove I09 when the pilot Hi5 rises.

Piston H33 of the fuel pressure control motor I0 operatively engages the end of a piston rod II3. A fuel pressure control lever I I4 is pivoted to piston rod H3 and to the pilot I 56 in a manner which will be apparent from Fig. 2. Pilot IE5 is shown in its 1ower-most position with free communication provided from header IEiI through conduit I88, groove I09, through the passage defined by pilot portion 1 I2 to the upper .set of ports and groove III, thence to conduit IE5 and the control oil pressure chamber I84.

When the powerplant starts, oil is supplied from pump 69 by way of these passages so as to build up a pressure in chamber I64 and a corresponding pressure in the control device of fuel pump 28. This pressure in chamber I05 will cause piston N73 to rise, and pilot I06 will also rise by means of the follow-up connection provided by lever I54. When pilot I06 blanks off the ports icommunicating with groove I09, the flow of oil 9. from header I I to the pressure chamber I 04 will cease. It will be understood by those skilled in the art pertaining. to hydraulic servo-devices that in order to have pilot I06 freely slidable in bush ing I07 a comparatively free fit is required, and that there will inevitably be a small amount of leakage through the respective clearances between pilot !06, bushing I01, and the cylinder in which bushing I0? rotates. There will likewise be some leakage in the hydraulic control device incorporated in fuel pump 28. Therefore, as soon as the supply of oil from header I0! to chamber I 04 ceases, this leakage results in a decreasing pressure in chamber I04 so that piston I03 tends to descend. Such movement of course causes pilot I06 to move downwardly and again provide communication by way of groove I09 so that oil' from header IOI can flow to the pressure chamber I04 and restore the pressure therein to its previous value. In operation, the pilot I06 is positioned by lever IM to meter the flow of oil from header IOI to chamber I04 at such a rate that a specific pressure is maintained therein, corresponding to the position of lever I I4.

"The control oil pressure in chamber I04 produces an upward force on piston I03 which is balanced by a main biasing spring II 5. This spring acts on the upper end of piston rod II3 through a variable ratio lever system consisting of a first lever IIt supported on a fixed pivot II! and a second lever H0 substantially parallel to lever H6 and supported on a fixed pivot II9 adjacent the free endof lever II 6. Roller I20 is arranged to transmit'force from lever [I0 to lever H8 and is adjustable in a direction substantially parallel to levers I I6, I I8 by a mechanism and for a reasondescribed hereinafter. This 10 effect of the spring I23, and lever I54 pivots clockwise about its connection with piston rod II3, so that pilot I06 is lowered to a position resulting in the admission of control oil from header IN to chamber I04 at a greater rate, with the result that the pressure maintained in chamber I04 is increased. i

It will be seen that in the absence of the other control devices described hereinafter, progressive clockwise rotation of the pressure control cam I24 would produce a continuously increasing pressure in chamber I04. The relation between the position of the cam I24 (i. e. the position of V throttle 54) and the pressure maintained in general arrangementis referred to as a nutcracker linkage and is somewhat similar to the arrangement used in our above-mentioned Patent No. 2,622,393. It will be apparent by analysis of Fig. 2 that if roller I20 is moved to the right, then the force exerted by spring I IE will produce a reduced reaction between lever IIS and roller I20, and a likewise reduced reaction between roller I20 and lever II 0. Because of the shift of roller I20 to the right, the reaction force lever II 8 imposed on piston rod H3 is still further reduced. Conversely it will be apparentfithat as roller I20 moves to the left, the reaction between lever IIS and roller I20 increases. Also the force exerted on piston rod II3 approaches closer to the value of the reaction force between roller I20 and lever H8. The roller I20 is arranged to be positioned by the compensating motor I2, as described hereinafter.

The pressure control lever I I4 is provided with an adjustable stop I2I biased into engagement with a vertically reciprocable rod I22 by means of a tension spring I23. The lower end of rod I22 is engaged by a contoured fuel pressure control cam I24 carried by the manual control shaft 5i. As indicated above, the piston I03 is shown in its lowermost position, while cam follower I 22 is in its uppermost position corresponding to the minimum pressure position of cam I 24. When the powerplant starts, piston I03 and pilot I06 move upwards, lever H4 pivoting about the adjustable abutmentIZI until the position of piston I03 pilot I 05, and the pressure in chamber I 04 reach a steady state condition corresponding to the minimum pressure position of cam I24. When cam I24 rotatesclockwise from its minimum pressure. position, rod I22 is permitted to move downwardly under the biasing chamber I04 can of course be made to vary according to any desired schedule by properly selecting the contour of cam I24. Thus it will be apparentthat any desired relation between fuel rate and throttle position can be obtained.

Speed responsive control The speed governing function of our regulating system is performed by the governor II This comprises an extension 80a of the driven shaft 80, which extension carries the gears 8|, 83. Shaft extension 80a is rotatably arranged in a central bore through a bushing I25 arranged to be rotated by means of the gear 81. At its upper end, bushing I26 carries a pair of pivoted flyweights I25 arranged to position a rotatable bushing I 21 relative to the slidable but non-rotatable speed control pilot l28. Bushing I2! is caused to rotate by reason of the engagement of fiyweights I25 with suitable sockets or grooves in its lower end portion. It is provided with an upper port aligned with an annular groove I29 in the wall of the cylinder in which bushing I2! slides and rotates. Likewise a lower port in bushing I21 communicates with annular groove I30.

The upper end of bushing I21 carries a suitable anti-friction bearing I3I which in turn supports a non-rotatable yoke I32. Seated on the cylindrical upper end of the housing I32 is a conical biasing spring I33 having at its upper end a button I33a engaged by bifurcated abutment I34 formed on one end of a pivoted lever I35. End portion I36 of lever I35 is arranged to be positioned by an actuating rod I31, the extreme position being determined by an adjustable stop I38. Rod I3! is provided with a springbiased telescopic slip joint I39, so arranged that the tworod portions I3'Ia and I3") are normally maintained in the relative position shown in Fig. 2. After rod I31, is in its uppermost position with lever end portion I35 engaging the stop I38, the slip joint I39 permits the lower portion I3Ib to move upwardly an additional increment, for a purpose noted hereinafter. The lower end of rod I3! is biased by the force of spring I33, into engagement with a speed recalibrating cam I40 carried on the manual control shaft 5|.

The slidable but non-rotatable speed control pilot I28 is provided with an upper yoke portion I28a through which projects a'pivoted follow-up lever I4I. A coil spring I42. concentrically arranged within spring I33 engages a fixed stop I43 which is freely slidable in lever end portion I34 and button I330! and adjustable by means of its threaded engagement with the fixed support, as shown in Fig. 2. It will be understood thatend portion I34 of lever I35 is bifurcated, with portions engaging cap [33a on either side of the stop screw I43. Spring I42 engages the yoked end portion I28a of the speed by a 'cap I41 and containing a coil spring I45,

arranged to' bias the piston I45 to its lowermost position, shown in Fig. 2. Connected to piston I46 is a rod I59 provided with axially spaced abutments I56, II and I52. The upper end of rod I49 is engaged by the free end of follow-up lever I II, under the influence of spring I42.

The abutment I56 on piston rod I49 is arranged to engage a bifurcated portion I53 at the extreme end of fuel pressure control lever II4. Likewise, abutment I52 is adapted to engage the end portion of a torque control lever I54, the

function of which will be noted hereinafter.

In operation, no control oil is supplied to the speed control piston E46 as long as pilot I28 remains aligned with the lower port in bushing I21 as shown in Fig. 2; and bushing I2I will remain so aligned as long as the speed of flyweights I25 corresponds to the speed setting established by the position of pilot I23, as set through the lever I35, rod I57, and speed recalibrating cam I46. If the rotational speed should rise above this established value, then fiyweights I25 move outwardly, causing bushing I2'I to rise and establish communication from groove I36 through the lower port in bushing I27 to the groove I26 and conduit I45. Control oil then flows from the header IIlI past the pilot I28 to the speed control piston I46 causing it to rise until follow-up lever I4I restores pilot I28 to the aligned position. Thus it will be seen that the speed control piston I46 moves upwardly in accordance with corresponding motion of the pilot I28. However, because the abutment I52 on piston rod I59 is somewhat spaced from the end portion I53 of fuel pressure control lever II i, such an increase in speed will not have an immediate effect on the fuel pressure. When the speed increases a preselected amount, as determined by the clearance between abutment I50 and lever end portion I53, then any further increase in speed will cause lever II4 to pivot counterclockwise about its connection to the fuel pressure control piston rod I I3. This causes the fuel pressure control pilot I96 to rise, reduces the pressure in chamber I54, and thereby decreases the fuel pressure produced by pump 28, as described above. Decrease in the supply of fuel to the combustors will of course produce a decrease in speed which permits flyweights I25 to move inwardly and bushing I2! to descend so that oil is bled through conduit I45, groove I 36, the lower port in bushing I21, and out through the open bottom end of the bore in bushing I2'I. The resulting decrease in pressure acting on speed control piston I46 causes it to descend under the influence of biasing spring I48 so that lever Il i moves downwardly until the adjustable stop I2I again engages cam follower I22. This action of the speed governor in reducing the supply of fuel to the combustors takes place irrespective of the position of control cam I24 and the actuating rod I22. Thus the speed governor II prevents over-speed 12 conditions regardless of the fuel pressure called for by the control cam I24.

Itwill also be noted that when the rotational speed is sufliciently high, as established by clockwise rotation of the speed setting cam I40, the fuel pressure control lever II4 will float free of; the actuating rod I22 and will be positioned by reason of the engagement between end portion I53 and the abutment I on the speed control piston rod I49. When operating in this manner, any decrease in speed below the established value will result in a lowering of bushing I21 by'flyweights I25 and bleeding of oil through conduit I45 to cause a corresponding descent of speed control piston I46 as described above. The rotating bushing I26 is provided with an upper port I and a lower port I56. The shaft 80a is provided with an axially extending groove or fiat portion I5I of sufficient length to communicate with ports I55 and I56 during a certain portion of each revolution. Since both shaft 86a and bushing I28 are rotating, theaverage percentage of the time during which the groove I5? is in communication with the two ports will depend on the geometry of the parts and the relative speed of rotation between shaft and bushing. This arrangement comprises a rotary flow restrictor which serves a purpose noted hereinafter.

Temperature responsive control Excessive temperatures in the powerplant are prevented by means of the temperature responsive device 42 which furnishes a signal to a temperature control motor I3. Motor I3 comprises a rotatable piston 13a arranged to reciprocate vertically in a cylinder defining a temperature control pressure chamber 131). Control oil is supplied that piston 13 forms a rotary flow restrictor for a second port I6'I communicating with a conduit I62, which also leads to the supply header IIlI by way of conduit I44and a shut-off valve I63 associated with the lower end portion I311) of the speed control rod I31. This shut-off valve comprises a rod portion of reduced diameter 53:: which is brought into alignment with conduit I62 so as to permit flow therethrough onlyunder certain special conditions described hereinafter.

Communicating with the temperature control pressure chamber 131) is the conduit 66 which is connected to the inlet port 49 of thermaldevice 42. During operation, oil is supplied from header IOI through conduit I58 past the rotary flow restrictor I59, I69 to chamber 131), and thence through conduit 66 to thermal device 42. As long as the temperature of the turbine exhaust gases are within the allowable safe limits, plunger 48 of thermal device 42 will remain in position to block the flow of oil from port 49. Therefore, a pressure is built up in chmaber 13b which holds the temperature control piston 13a down against the bias of spring I65. If, however, the temperature should rise, differential expansion between the metal tube 43, and quartz rod 44 of thermal element 42 will cause the cantilever spring 46 to relax, thus permitting plunger 48 to move away from port 49 so that oil may be discharged therefrom and th pressure in chamber 13b reduced. This results in upward movement of piston 13a under the influence of biasing spring I65, and if this upward movement continues far enough the temperature piston may take over control as follows.

It will be seen from Fig. 2 that a rod I66 connected to piston 13a is provided with an end portion engaging one arm of a pivoted lever I61, which has a second arm arranged to exert a down?- ward force on torque control lever I54. An intermediate portion of rod I66 forms an annular.

shoulder I58 which is arranged to engage an abutment I69 fixed to the actuating rod I22. It will be apparent that if temperature control piston 13a moves upwardly far enough, the shoulder I60 will engage abutment I59 and cause rod I22 to move the fuel pressure control lever H4 in a counter- Torque responsive control The arrangement for controlling the propeller shaft torque will now be described. As noted above, regulator shaft 681) is connected to the propeller pitch control lever 32, the arrangement being such that clockwise rotation of shaft 68?) produces an increase in the angle of pitch of propeller blades 3|, which results in an increase in propeller shaft torque. Shaft 68b carries a gear sector 68a having teeth which project into the cylinder of pitch control motor 14 and engage rack teeth formed in the outer surface of piston 14a.

The pitch control piston 14a is arranged to be positioned by control oil admitted to end pressure chambers 14b and 140, respectively, by means of pitch control pilot I10. The lower end of pilot I is arranged to be subjected to the pressure of the oil in the torque-sensing cylinder 34, being placed in communication therewith by conduit 62. The force exerted on pilot I10 by the oil pressure communicated by conduit 62 is balanced by a force exerted by a spring I1I through a lever I12 having an end portion engaging the upper end of a vertically slidable rod I13 with a lower end portion I14 engaging freely the upper end of the rotating and sliding pilot I10,. An adjustable roller I15 forms a variable fulcrum arranged to be positioned by the compensating mechanism described hereinafter.

The reaction force between roller I15 and lever I12 may be varied by means of a pivoted lever I16 which engages roller I15 on the side opposite from lever I12 and is arranged to be positioned by means of a gear meshing with a reciprocable rack I11 connected to a slidable torque setting rod I18.

lever I12 to move downwardly and further compress spring I1I. Compression of spring I1I of course increases the spring force on lever I12, thereby increasing the reaction force imposedby lever I12 on the upper end of rod I13. The increased force on rod I13 will first tend to move pilot I10 downwardly from its aligned position with the ports leading to conduits I82, I83 so that control oil is supplied from header IDI through conduit I to the chamber IBI formed by the reduced diameter portion of pilot I10, thence through conduit I82 to the upper end chamber 14b of the pitch controlmotor. Meanwhile downward movement of pilot I10 has opened communication between the lower end chamber 140 through conduit I83 and out past the pilot I10 by way of an axial groove I 83 formed in the wall of the cylinder in which pilot I10 slides. The increased pressure in the upper end chamber 14b combined with the reduced pressure in chamber 140 causes the pitch control piston 14a to move downwardly and rotate gear sector 68a counterclockwise to call for increased propeller pitch. As noted before, increased pitch means increased propeller shaft torque when the speed governor 1I holds the rotational speed constant.

In the event that the propeller shaft torque increases above the value for which the regulator is set, the pressure communicated through con-' duit 62 to the lower end of pilot I10 will increase, with the result that the pilot moves upwardly to admit control oil from header IOI to conduit I83 and the lower end chamber 140 of the pitch control motor. "Simultaneously oil is bled from the upper end chamber 14b through conduit I82 and out through a drain port I84. Pitch control piston 14a thereupon moves upwardly to rotate shaft 60?) clockwise so as to call for decreased propeller pitch and therefore decreased torque. A light spring I8 Ib, just stiff enough to overcome the weight and friction of the moving parts, is arranged to bias the pilot I10 to its uppermost position, shown in Fig. 2, when the powerplant is inoperative.

Connected to pitch control piston 14a.is a follow-up rod 14d freely slidable through the upper end of the pitch control motor cylinder, and having an end portion 146. A'spring I1Ia arranged between the end portion 14c and the lever I12, as shown, introduces a feedback force" in the torque governing mechanism which has been found to produce a desirable stabilizing effect.

The torque modifying lever I54 changes the op- I86. A coil spring I81 is arranged around rod I13 and engages the upper surface of bushing ing I and the lower surface of lever I112. With this arrangement, clockwise movement. of the torque modifying lever I54 will produce upward movement of abutment I85 so as to compress spring I81 and produce an upward force on the left-hand end of lever I12. Such upward force reduces the reaction imposed downwardly on the rod I13 by the biasing spring HI and lever I12. Thus it will be seen that clockwise rotation of lever I54 will unload or reduce the downward force imposed on rod I13, and thus reduce the propeller shaft torque setting.

ama e The pitch control motor I4 is arranged to hold constant the propeller shaft torque at a value determined by the manually controlled cam I'ie, as modified by the compensating arrangement through which roller H5 is positioned, and the overriding devices acting on the torque governor through the modifying lever l5 i.

Compensating mechanism j As in the regulating system disclosed in our U. S. Patent 2,622,393, means are provided for automatically modifying the action of the regulator so that the full load rating varies in a predetermined manner as a function of thealtitude or inlet conditions, the fuel supply rate being less for full load operation at high altitudes than at sea level. The compensating mechanism is also arranged so that any given position of the operators throttle 54 corresponds at each altitude to a predetermined percentage of the full load rating permissible at that altitude. This contributes to the pilots ease of operating the powerplant for he knows that, for instance, the threequarters throttle position will produce per cent of full rated load, regardless of changes in inlet conditions and the fact that the permissible full load rating varies as a function of altitude. In the present regulator, the compensating mechanism also incorporates means for recalibrating the torque control mechanism so that the torque setting called for by cam lid is automatically modified as a function of altitude and other pressure conditions associated with the operation of the powerplant.

The compensating motor i2, which is arranged, to position the variable fulcrums ms and its is.

energized by control oil from header Iili directed by the compensating'pilot I56, as positioned by a pair of pressure responsive bellows I9! and IE2. Bellows IElI has an upper end fixed by suitable means to a support I93 and a movable head Iiii with a rod I95 pivoted to a lever I85. Inside bellows I9! is a tension spring I9? connected to a hook secured in the movable head I94 and an adjustable rod I93 secured in the fixed end member I99. It will be apparent from Fig. 2 that the tension of spring I9? may be adjusted by removing the cover 280 and rotating the adjusting nut 2B1. The pressure obtaining in the outlet Id of compressor I is communicated to the interior of bellows I El by a conduit 65. 'Bellows I 92 is connected to lever ice in opposition to the bellows I9! and has its interior communicating with the pressure existing at the inlet 5 of compressor I by means of conduitt i.

Because the compressor inlet pressure varies as a function of altitude, thisrbellows arrangement will be responsive to changes in altitude. Furthermore, since the compressor discharge pressure is a function of compressor inlet temperature, and also a function of compressor efficiency, the bellows arrangement will be responsive to these factors.

As will be apparent from Fig. 2, the lever I95 is pivotally connected to the compensatingpilot I90 and to the piston rod i222 associated with the piston 12a of the compensating motor. In operation, control oil is supplied from header IIiI through conduit 262, through an annular groove in the rotating bushing 263 to one or more ports 264 which are blocked by disk 285 of pilot I96 when the compensating mechanism is in a steady state condition. In the event of a change of conditions resulting in an upward movement of rod I95, for instance a decrease in compressor discharge pressure (for instance that resulting from an increase in altitude) lever E95 will pivot clockwise about its connection with piston rod 72?), causing pilot let} to rise, so that oil is admitted from conduit IiJI through conduit 252 and port 254 to the lower side of pilot disk 205. thence through ports 255 to conduit 237 and the chamber of compensating motor 12 on the lower side of piston 12a. The resulting increase in pressure causes piston 52a. to move upwardly until pilot Iiiil is restored to its neutral position by means of the follow-up connection provided by the lever I55. Liquid contained in the chamber above piston lza passes directly through conduit 258 to the pilot I98 past the check valve 2ll9,and out drain port 2i2a and vent 2 Hi).

Conversely when increasing compressor discharge pressure causes the rod I95 to move downwardly, pilot I95 descends so that oil is conducted through conduit 252 and port 294 to the upper side of pilot disk 205. Because of the check valve 269, it must pass'to the upper side of piston 12a by way of the conduit 2II the rotary flow restrictor formed by the parts I55, I56 in bushing E26 and the axial groove in shaft 86a, thence through conduit ZIIl. Increase in pressure on the upper side of piston 72a causes it to move downwardly until pilot I is restored to its neutral position, liquid from the lower end chamber of motor 72 draining through conduit Bill directly to the port 206 and out by way of drain port 266a and vent 20Gb.

With this arrangement it will be seen that when compressor pressure rise decreases, pilot I90 moves upward to cause control oil to be supplied to the lower surface of piston 12a, the piston responding promptly. On the other hand, with increasing compressor pressure rise pilot I55 moves downwardly to admit fluid to the upper side of piston 12a at a limited rate past the rotary flow restrictor I55, I56, I51.

Upward movement of piston rod 1% causes a cam follower roller 2I3 carried on a pivoted link 2 I4 to be positioned along a stationary cam member 2i 5. A second roller 2I6 is carried by a member 2I'l pivoted to link 2M and biased into engagement with the opposite side of cam member 2I5 by means of a spring 2I3. The function of the spring-biased roller 2 I6 is merely to maintain the cam follower 2 I3 in engagement with the cam member H5. The previously mentioned roller I20 is carried by a link 2I9 pivoted to link2I4 at the axis of cam follower iii-i. It will be apparent from Fig. 2 that upward movement of piston rod 721) will cause link El i to move upwardly and clockwise as roller 2 3 follows the surface of cam 2I5. Roller I20 is thus caused to move to the right so as to reduce the reaction force exerted by spring II5 on rod H3. While Fig. 2 shows the cam member 2 :5 as having a straight uppersurface inclined at about 45 degrees to the horizontal, it will be obvious that member 2I5 may be inclined at other angles and may have a curved rather than a straight surface so as to position roller I2ll according to any desired schedule as a function of the vertical movement of rod 121). Thus the compensating eiiect produced on the fuel pressure control piston Hi3 can be made to vary in any desired manner.

Piston rod 121) is also provided with a laterally I is carried by an arm 224 pivoted to link 220' and biased by a spring 225, into engagement with the under side of. cam "member 222. The adjustable roller I is connected bymeans of link 226 to the link 220, so that vertical movement of member 120 serves to position the roller 15. .Cam member .222 may also inclineatvarious angles or have various 'curvedshapes so as to produce any desired movementof the roller I15 as a function of the movement of the compensating piston 12a. I I r By appropriate shaping of cams 2I5 and 1222, the compensating mechanism canbe arranged to produce a preselected percentage of rated power. output for each position of the throttle,

irrespective of changes in inlet conditions, al-

titude, compressor efliciency, etc.

Operation 7 As indicated above, Fig. 2 represents the regu lator 29 when in the off or shut-down condition. To start the powerplant, the starter motor 26 is energized so as to cause the powerplant rotor and the propeller to turn. In order to decrease the starting torque required of motor 26, it is desirable that the propeller blades 3I be positioned tothe zero angle of attack. To effect this, when cam I19 returns to the noload position biasing spring I8Ib1 will cause the pitch control pilot I10 to move to its uppermost position, shown in Fig. 2, causing the pitch con trol piston 14a to rise tothe 'zero pitch position. y,

After the starter motor has brought the powerplant rotor up to a speed of approximately 10 per cent of its rated speed, the throttle handle 54 may be moved forward from the off position to rotate the manual control shaft 5I clockwise. During about the firstfive degrees of such rotation, the link 55 (Fig. 1) causes the shut-off valve 51 to open. Meanwhile, rotation of the compressor-turbine rotor has caused the pump 69 in regulator 29 to supply control oil under pressure to the conduit IOI and thence to the various components of the regulator. Control oil will flow "through conduit I00 to the pitch control pilot- I10, through conduit I03 to the lower chamber 140 so as to bias the pitch control piston 14a 'to its uppermost position, corresponding to the zero pitch'position of the propeller. Thus the regulator assures that the propeller will be in thezeropitchor minimum torque position during the startingcycle.

Likewise control oil will flow through conduit I08 to the ports I09 of the fuel pressure control pilot I 06, thence through conduit I05 to the control device of fuel pump 28 and to chamber I04 of the fuel pressure control motor 10. Thepressure in chamber I04 causes piston I03 to rise slightly from the lowermost position shown in Fig. 2, so as to float free of the shoulder which defines its lowermostposition. This slight upward movement of piston I03 causes the fuel pressure control lever IM to rotate clockwise about the stop I2 I, thereby raising the fuel pres sure control pilot I06 so as to shut off the flow of control oil through port I09. Actually, the pilot I96 will take such a position as to permit a limited rate of flow through port I09 to conduit I05 so as to maintain a constant pressure in the chamber I04, this minimum pressure corresponding to the zero discharge condition of the fuel pump 28. I

If now, the manual control shaft 5I is caused to rotate still further in a clockwise direction, the fuel pressure control cam I24 will permit the cam follower I22 to move downwardly under the influence ofbiasing spring I23, which also serves to move the fuel pressure control lever I I4 clockwise about its pivotal connection with the rod I I3. Such movement of lever II4 causes pilot I06 'to descend so as to increase the flow of oil through port I09 ,to conduit I05 and the chamber I04. The resulting increased pressure in chamber -I04 causes the piston 503 of the fuel pressurecontrol motor 10 to rise, and to simultaneously causethe pump 28 to produce an increased discharge pressure. When the fuel pressure in the nozzle supply line II rises to the prop:

er value, of the order of 40 pounds per square inch, the ignition devices (not shown) initiat combustion in the combustors 3. If the manual control shaft 5I moves still furtherclockwise, the fuel pressure control cam I24 I duit I I, with the result that the rotational speed of the powerplant increases correspondingly. Durin this increase in speed, the flyweights I25 of the centrifugal speed governor 'II :move progressively outward and raise the bushing I21 so as to admit control oil from conduit I44 through port I29, thence through port I30 to conduit I45 and the lower surface of the speed control piston I46. This hydraulic pressure on piston I46 causes 7 it to progressively rise as the rotationalspeed of the powerplant increases, until at the speed of about 60 per cent of the rated speed the abutment I50 on piston rod I49 just engages the bifurcated end I53 of the fuel pressure control lever .II4. With any further increase in rotational speed, piston I46 will move lever II 4 upwardly so that the stop I2I is lifted free of the cam follower I22. Thus at about 60 per cent of rated speed, the speed governor 1I takes over the control of the fuel pressure from the manual pressure setting cam I24. I

From this point on,the rotational speed is further increased by recalibrating the speed governor H, as follows. Clockwise rotation of the speed recalibrating cam I40 causes the cam follower rod I31 to rise, rotating lever I35 counterclockwise and compressing the conical spring I33. The increased downward force causes bushing I21 to descend so that control oil is drained through conduit I45 and the pressure on the speed control piston I 46 decreases, causing the piston todescend and fuel pressure control lever M4 to drop so as to lower pilot I06, increase the flow of controloil from conduit I08 to conduit I05 and thereby increase the discharge pressure of. pump 28. This increased fuel supply pressure results in increased rotational speed of the powerplant rotor. Thus as the speed control cam I40 rotates clockwise, the fuel supply to the combustors progressively increases, with a corresponding increase in rotor speed to the rate value.

It may be noted that the shape of the fuel pressure control cam I24 is so selected that during control of lever II4 by the speed governor 1I there is maintained a predetermined clearance space between the surface of cam I24 and the end of cam follower I22. The presence of the cam follower I22 restricts movement of lever II4 downwardly in the event an abnormally large transient speed condition should cause the gover- '19 nor 1| to call for a sudden downward movement of lever II4. Thus when speed governor 1| is in control, the. cam I24 and follower I22 constitute an automatically adjustable stop for limiting to a preselected displacement any sudden movement of lever H4, in the increase fuel direction. The amount of such sudden displacement which will be permittedmay of course be varied by adjusting. the screw -I2I. This arrangement 7 produces a stabilizing action on the speed governing means, preventing sudden large increases in the fuel supply with resultant excessive rise a in temperature.

Throughout this starting cycle, corresponding to total clockwise rotation of shaft of about 40 degrees, the propeller blades 3I are atzero' pitch and the powerplant is producing no useful shaft horsepower. If now shaft 5| rotatesclock wise still further, cam I19 begins to move fol lower I18 upwardly,. causing lever I16 to rotate counterclockwise and depress roller I and lever I12, thus compressing springs I1 I, I H a, andproducing a downward force on rod I13.. This causes 7 result thatthe hydraulic pressure in chamber 31 of the torque sensing cylinder 34 is increased. This increased pressure, communicated through conduit 62 to the lower end of the pitch control pilot I18 causes the pilot to rise so as to decrease the flow of control oil from conduit I80 to the upper'chamber 14b of the pitch control motor 14.

Thus it will be seen that clockwise rotation of the torque control cam I19 produces a downward movement of the pitch control pilot I10, the pilot being restored by the resulting increased pressure signal produced by the torque sensingcylinder 34. 'Spring I1Ia is permittedto extend, by the downward movement of piston 14a, thus introducing a restoring action by decreasing the force on lever I12, decreasing the downward force on pilot I10, and thereby tending to reduce the torque called for. r

If propeller shaft torque should increase, the pressure signal communicated through conduit 62 to the lower end of pitch control pilot I10 will likewise increase, with the result that the. pilot will rise, admit control oil to the lower chamber 140 of the pitch control motor, thereby producing a decrease in the propeller pitch with a consequent decrease in torque to the value corresponding to the position of the torque setting cam I19. Similarly a decrease in propeller shaft torque would result in a decrease of pressure in conduit 62, causing pilot I10 to descend and control oil to be admitted to chamber 141) so as to move piston 14a downwardly in the increase pitch direction. 7

Thus it will be seen that the regulator maintains the propeller shaft torque constant at a preselected value determined by the angular position and contour of the torque-setting cam I19. Meanwhile, the speed governor'1l has kept the rotational speed of the powerplant constant by regulating the rate of flow of fuel to the combustors as described above.

As also describedabove, the torque modifying lever IE4 is arrangedto compress spring I81 so as to: exert' an upward: force: on lever I12 and thereby decrease the downward force exertedby spring I11 on the. torque? control rod". I13: To

effect this unloading action, thelever H4 is arranged to be moved: clockwise .aboutv fixed .pivot I54a, eitherby counterclockwise movement of lever I611, .as: actuated by the temperature. con.- trol motor 13 or by: downward movement of: abutment I52 on the'speed' controlv piston rod I49.

The operation of the temperature controlimotor 13' is as follows; When the powerplant. starts, with the thermal device 42: cold; the; plunger. 48 of the vthermal'device completely blockstthe flow of oil through port;49; and therefore oil supplied through conduit I58 to the temperature control motor causes pressure to buildup in. chamber 13b. This pressure causes the temperature control piston 13a to move downwardly against the bias of spring, I85, permitting lever I61 torotate clockwise so: that it exerts no forceonlever I54. When speedgovernor H is inactive, with the fuel pressure being. controlled by cam I 24 acting on lever I'I4',.the.speed.control piston. I46 is in 7 its lowermost. position, as shown in Ei'g. l. The abutment I52 on piston rod. I49. holds down the right-hand end of torqueemodifyinglever. I54 so that. spring I81 is compressed and in the torque unloading condition. When the powerplant speed rises to thepointwhere speed governor 1| assumes control,. oil' pressure acting on. piston I46 causes piston rod I49 to rise so that. abut;-

ment I52 moves free of'the bifurcatedend [54b of thetorque-modifying lever I54. This permits the left-hand end' I54'cof'lever I 54 to move down? Wardl'yinto engagement with thestop I8'6',so that the. unloading spring I81. is permitted to extend toitsminimum.forceposition.

As the temperature of. the turbine discharge gases. increases, the plunger 48 of. the thermal device. 4'2 permits a progressive increase. in the flow ofQcontrol oil through the. port. 49, with'the resultthat the oil. pressure. inchamber 13b of the temperature control motor 13 decreases, and piston13arises under the influence of biasing. spring I65. As the'piston rod I66 rises, lever I61. moves counterclockwise to produceaclockwise. turning movement of .the torque-modifying lever I54; vAs notedabove, this results in compression of spring I81 so as to-reduce the downward force exerted onthe pitch control pilot. I13. Thus, when excessive temperatures actuate the thermal device I called for by-v cam I-19- in the event that the cam calls for a torque whichwould result inanexcessive temperature level. i r

In the. event of abnormal underspeed conditions, thespeed control. piston I45 will descend until the abutment I52. engages the end portion I541) of the tqrqueemodifying. lever, moving, the latter clockwise. This. also-compressesspring I81 and decreases the torque setting. Thus, if the manual control-shaft 5|: should be-p'ositioned to call for increasing torque when: the rotational speedof the powerplant is below normal rated speed, the torque setting will be automatically adjusted to-a value suitable for the reduced speed condition. q

In: further connection with the; operation of the temperature control motor 13, it shouldbe noted that. while. the initialrise of the temperature'controlpiston 13a acts through lever I61 on the torque-modifying lever I-54-,, the. piston rod constant.

ment I89 so as .to act directly on the fuel pressure control lever 'I I- L moving it upwardly to decrease the fuel. supply. 1 Furthermore, motor 13 will thus act. on lever H4 during the starting cycle, when the pitch setting isv zero, and therefore action of rod I66 on lever I54 through lever I 51 would have no effect on the system.

Also in connection with the temperature control motor 13 it willbe noted that oil can enter chamber 13b from supply conduit I58, at only a limited rate by reason of the action ofgthe rotary flow restrictor I59, I60. Thus, when plunger 48 of the thermal device 42 moves in a direction to block port 49, as gas temperature decreases, the pressure in chamber 13b of the temperature control motor can increase'only at a limited rate. On the other hand when the thermal device 42 acts, by reason of a sudden increase in the temperature level, to decrease the oil pressure in chamber 13?), the temperature control piston 13a responds immediately. With this arrangement, the temperature level at which the powerplant operates may be increased only at a predetermined limited rate; whereas the temperature regulating means responds immediately to decrease the fuel supplyin the event of an increase in temperature. This is extremely important from the safety standpoint.

The action of the temperature control motor 13 is further modified under certain conditions by the admission of oil through conduit I62 bythe action of the valve I63. After the speed-setting cam I40 is positioned to call for the normal rated speed, in which condition the end portion I36 of lever I35 will be in engagement with the adjustable stop I38, a certain additional increment of rotation of the manual control shaft 5| will cause the portion I311) of push rod I31 to move upwardly relative to the portion I31a, this action being permitted by the spring biased telescopic connection I39. This over-travel of portion I31b brings the reduced rod portion |63a intoalignment with conduit I52 so as to permit flow of additional oil from conduit IM to port IBI associated with flow restrictor, I60. Control oil will then be supplied to the temperature control motor 13 through both conduits I62 and I50. This will result in an increased pressure being maintained in chamber 132), for a given condition of the thermal device 02, so that the temperature control piston 13a will assume a somewhat lower-thannormal position. Thus while the speed setting is held constant, causing governor TI to maintain normal rated speed, the manual control shaft 5| is permitted to rotate clockwise an additional increment so that the torque setting cam I19 can call for an additional increment of shaft horsepower output, asmay be required in emergency situations, the temperature control motor 13 being temporarily recalibrated so as not to prevent such an increase in output.

The operation of the compensating motor 12 is as follows. As indicated above, the supply of control oil to the compensating motor 12 is controlled by the compensator pilot I90 as positioned by the pressure responsive bellows I9I, I92. Bellows I9I is responsive to compressor discharge pressure, the value of which is a joint function of compressor inlet conditions and rotational speed of the compressor.- Also, if the compressor efliciency decreases,

pensator piston 12a.

as by reason of the compressor blading becoming dirty, the discharge pressure will decrease, other factors remaining Since the inlet temperature and pressure vary as 'a function of altitude, the bellows combinationIBI, I92. will also be responsive to altitude. In normal operation the governor II will maintain. the rotational I speed, constant,

therefore the'compensating motor 12will be actuated in accordance with inlet conditions (as affected by changes in altitude, etc.) and will also tend to compensate for changes incompressor emciency, which has a verymaterial influence on the operation of a gas turbine powerplant of the type described. i a

In the event of a decrease in compressordis charge pressure (or an increase in altitude) bellows I9I will collapse somewhat causing lever I96 to move clockwise about .its pivotal connection with piston rod 12b. This will raise the compensator pilot I admitting oil fromsupply pipe 202 to the lower side of compensator piston 12a by way of ports 204, 205, and conduit 201.

The increased pressure on the lower side of piston 12a will causerod 12b to rise until compensator pilot I90 is restored to the position in which disk 205 again blocks port 204. Upward movement of piston rod 12b will cause the variable fulcrum roller I20Jto be positioned to the right so as to effect a decrease in the downward force exerted on piston rod II3 by the main biasing spring II5, as described above. The decreased downwardforce on rod II5 permits piston I03 to move upwardly so that the fuel pressure control pilot I06 is caused to rise and decrease the control oil pressure in chamber I00 and conduit I05, resulting in a corresponding decrease in fuel pump discharge pressure. Thus it will'be seen that the discharge pressure of fuel pump 28 is decreased as altitude increases to automatically provide the decreased fuel rate required for high altitude operation.

Conversely, a decrease in altitude (increase in compressor discharge pressure) causes the bellows I I 9| to extend, lever I96 moving compensator pilot I90 downwardly to admit oil from the supply conduit 202 to ports 204, 2I2, through conduit 208 past the check valve 209 tothe upper side of com- The resulting downward movement of piston rod 12b causes the adjustable fulcrum roller I20 to move to the left to increase the downward force produced on piston rod II3 by spring I I5, and thereby increase the discharge pressure of the fuel pump 28.

Upward-movement of the compensating piston 12a, corresponding to a decrease in compressor discharge pressure, likewise causes the variable fulcrum roller I15 to move to the right. As noted above, this results in a decrease in the force of the lever I12 on the rod I13, thereby decreasing the propeller pitchand the shaft torque. Thus the. propeller torque and shaft horsepower output are automatically decreased at higher altitudes, corresponding with the decreased fuel rate effected by the nutcracker linkage H6, I20, IIB.

Conversely, an increase in compressor discharge It will be seen that the fuel pump discharge.

pressure, and therefore the rate at which fuel is supplied to the combu'stors, and thepropeller shaft torque are automatically varied ,so thatthe ports2I2.

normaiwwer output decreases as a preselected under side of compensating piston 12a. The piston moves upward promptly because the oil trapped above it is free to return past check valve 209 through: conduit 268 to ports H2 and (meme drain port 2I2a and vent 2I2b. Therefore the compensatin action introduced by the bellows I9I, I92 takes place promptly for a decreasing compressor pressure level. a

On the other hand, when compressor discharge pressure increases, as in a rapid descent r dive,

or due to other causes such as an increase in.

compressor speed, the compensator pilot will move downwardly to admit oil from conduit 202 to the Because check valve 289 prevents supply of oil directly to the upper surface of piston 12a through conduit 268, it must flow by way of conduit 2I I, the rotary flowv restrictor I55, I56, I51, thence through conduit 2 it. By this means, the rate of movement of the compensating piston downwardly is limited to a preselected value. In other words, the compensating action of motor I0 can take place only at alimited rate when the compressor pressure level increases. the. important effect of preventing an excessive rate of increase in the temperature level due to too rapid increase in the fuel supply caused by sudden increases in compressor discharge pressure.

To facilitate reference in Fig. 2, arrows have This --has follower: I22 with a preselected clearance space therebetween. Further rotation of manual control shaft ill in its normal operating range causes th speed governor II to be recalibrated by cam I so as to maintain a progressively higher speed until lever I35 engages the adjustable stop I38' corresponding to the normal rated speed; Whenthe speed reaches about 90 per cent of its normal rated value, the torque setting cam I19 actuates the propeller pitch control motor I4 to adjust the blades to a positive angle of attack. This causes an increase in the propeller shaft torque. above its minimum value, so

that useful horsepower output is produced. Still furthermovement of manual control shaft 5| in the normal operating range causes the cam sudden increase in gas temperature, the tempera 'tur control piston 13a will promptly rise to first decrease the torque setting by action of the lever been added to indicate the direction of flow in V hydraulic lines, as well as the direction of movement of the various mechanical parts; Thus, the arrow adjacent piston rod H3, accompanied by a plus sign, indicates that the rod moves in the direction indicated for an increase in fuelpump discharge pressure. Similarly the arrow adjacent conduit III5, with a plus sign, indicates the direction of control oil flow corresponding to an increasing fuel I rate. The arrow adjacent lever I61, with a; minus sign, indicates the direction of motion for decreased torque setting. The counterclockwise arrow on pitch control shaft 68, with a plus sign, indicates the increase pitch direction ofmotion; the plus arrow on manual control shaft 5! indicates the fincrease fuel motion,

etc.

The integrated operation of an aircraft gas turbine powerplant having our improved regulating system may be summarized as follows.

During the starting cycle of the powerplant,

the rotor i accelerated from rest by meansof an auxiliary starting motor. When the speed has arisen to'approximately 10 per cent of its rated value, the throttle is actuated through its start-' ing speed range to rotate the manual control shaft 5I- so that the fuel pressure control cam I24 positions pilot I06 to call for increasing fuel pump discharge pressure. When the fuel pressure reaches the proper value, the ignition system initiates combustion in the combusto'rs 3. Further movement of the throttle handle causes the fuel pump discharge pressure to be controlled directly by cam I24. pressure can be increased until the speed rises toabout 60 per cent of the normal rated value. Atthis point the speed governor lI assumes control and the abutment I2'l floatsfree of the cam By such control the fuelv IE? on the torque-modifying lever I54, and will subsequently act directly through abutment I89 on the fuel pressure control lever I I4 to decrease the fuel pump discharge pressure and reduce the temperature level to a safe limit. An increase of the temperature level is permitted by the thermal device 42 and the temperature control motor 3 at only a-limited rate, by reason of the flow restricting device incorporated in the temperature control motor. A temperature level in excess of the normal limit is permitted when the control lever is moved into its over-travel position to secure extrapower in an emergency. 'Both the fuel pressure control mechanism and the propeller shaft torque control mechanism are automatically recalibrated so that the normal rated output varies in a desired manner as a function of compressor discharge pressure, compressor efficiency, altitude,,etc. Sudden decreases in the pressure level at which the compressor operates are promptly compensated for, while with in- V of operating, conditions.

While our invention has been specifically de- SCIIbK-Zd as applied to a gas turbine powerplant for aircraft applications, it will be apparent that it may also be applicable to other gas or steam turbme prime -mover powerplants for marine propulslon, locomotive applications, or for other uses.

Letters Patent 0f the-United States, is; I

where V Whatwe claim as new and desire to secure by 1. In regulating apparatus for a powerplant including a prime mover arranged to drive an adjustable torque load device, means responsive to torqu for controlling the load device to maintain the torque substantially constant at a selected value, speed responsive means for controlling the supply of operatingmedium to the prime mover to maintain rotational speed substantially constant at a selected value, adjusting means for modifying the action of the torque control mean to select the torque setting, and adjusting means for modifying the action of the speed control means to select the speed setting, the combination of stop means for determining the maximum speed setting of said second means, means responsive to a temperature condition appurtenant to the operation of the powerplant for modifying the action of the torque and speed control means to prevent excessive temperatures, a common control member having a normal operating range and an emergency over-travel range, means con nected with the control member for actuating the torque and speed control meanslin the normal range, the speed adjusting means including means adapted to effect movement of the control member into the over-travel range with the speed setting held constant by said stop, and means connected with said last-mentioned means for modifying the action of said temperature responsive means to eifect emergency operation at temperatures abovethe normal limit.

2. In regulating apparatus for a powerplant including a prime mover arranged to drive a variable load device, means including a speed governor for controlling the supply of operating medium to the prime mover to maintain rotational speed substantially constant at a selected value, and adjusting means for modifying the action of said operating medium control means to determine the speed setting, the combination of stop means defining the maximum setting of said speed adjusting means, means responsive to a temperature condition appurtenant to the operation of the powerplant for modifying the action of said operating medium control means to prevent excessive temperatures, a control member having a normal operating range and an emergency over-travel range, and means connecting the controlmember with said adjusting means and including means for effecting movement of the control member into the over-travel range with the speed setting held constant at th value determined by said stop, and means associated with said connecting means and adapted to modify the action of said temperature responsive means to effect emergency operation at temperatures above the normal limit when the control member is in the over-travel range.

3. In regulating apparatus for a gas turbine propulsion powerplant with a rotor driving an adjustable pitch propeller, torque responsive 26 sponsive device for positioning said abutment whereby the setting of the torque responsive means is automatically decreased upon a decrease in rotor speed below the normal rated value.

4. In regulating apparatus for a gas turbine propulsion powerplant with a rotor driving a variable pitch propeller, means for automatically controlling the propeller pitch to maintain torque supplied to the propeller substantially constant at a selected value, and means responsive'to rotor speed for automatically controlling the supply of fuel to the powerplant to maintain rotor speed substantially constant, the combination of means engaging and exerting a biasing force on the pitch control means in the direction to reduce said selected value, means responsive to a temperature condition appurtenant to the operation of the powerplant, means positioned by said temperature responsive means connected to said biasing means means for automatically controlling propeller pitch to maintain the propeller torque substantially constant at a selected value, and means responsive to rotor speed for automatically controlling the supply of fuel to the gas turbine to maintain the speed substantially constant at a preselected value, the combination of spring biasing means engaging the torque responsive means and urging said means in a direction to reduce said selected torque value, movable abutment means engaging said biasing means whereby the force exerted by the biasing means on the torque responsive means may be varied, and means connecting said abutment means to the speed refor varying the force thereof whereby said pitch control means is caused to move in a direction to decrease said selected torque value upon a predetermined rise in temperature, and means p0sitioned by said temperature responsive means connected to the fuel control means to reduce the fuel supply upon a predetermined further rise in temperature.

5. In regulating apparatus for a gas turbine propulsion powerplant with a rotor driving a variable pitch propeller, means for automatically controlling the propeller pitch to maintain propeller torque substantially constant at a selected value, and means responsive to rotor speed for automatically controlling the supply of fuel to the powerplant to maintain rotor speed substantiallyv constant, the combination of means engaging said pitch control means and adapted to exert a biasing force thereon in a direction to reduce said selected torque value, movable abutment means positioned by the speed responsive means engaging said' biasing means for varying the force exerted by said biasing means on said pitch control means whereby said selectedtorque value maintained by said pitch control means is automatically decreased upon a decrease in rotor speed below the normal rated value, means responsive to a temperature condition appurtenant to the operation of the powerplant, means positioned by said temperature responsive means also engaging said biasing means for varying the force thereof exerted on said pitch control means whereby a decrease in said selected torque value is effected upon a predetermined rise in temperature, and means positioned by said temperature responsive means connected to said fuel supply control means to reduce the fuel supply-upon a predetermined further rise in temperature.

6. In regulating apparatus for a gas turbine propulsion powerplant with a rotor driving a variable pitch propeller andhaving a starting speed range and a normal operating speed range, means for automatically controlling propeller pitch to maintain propeller torque substantially constant at a selected value, fuel supply means including regulating valve, means responsive to rotor speed connected to said valve means for automatically controlling the supply of fuel to the powerplant to maintain speed substantially constant at a selected value, said speed responsive means being operative only at speeds in the nor mal range, the combination of a common controlsponding to the normal operating speed range, firstmeans connecting the control-member to the torque control means to maintain the torque setting at a minimum value in the initial range of positions of the control member, second means connecting the control member to the speed responsive means to progressively increase said selected value through the initial and intermediate range of positions of the control member, and third means connecting the control member directly to said valve means, means whereby the rate of fuel supply is controlled in the initial range of positions of the control member where the speed governor is inoperative.

7. Regulating apparatus in accordance with claim 6 and including means responsive to a temperature condition appurtenant to the operation of the gas turbine connected to the pitch control means to decrease said selected torque value automatically upon a predetermined rise in temperature when rotor speed is in the normal operating range, and means actuated by said temperature responsive means connected to said regulating valve means to reduce the fuel supply upon a predetermined further increase in temperature.

8. In regulating apparatus for an aircraft gas turbine propulsion powerplant including a compressor arranged to induct ambient air, a'combustor, a turbine with a shaft arranged to drive. a variable pitch propeller, means for automatically varying the pitch of the propeller to maintain shaft torque substantially constant at a selected value, and means for controlling the supply of fuel to the combustor, the combination of automatic compensating means including a first device responsive to compressor inlet pressure, a second device responsive to compressor discharge pressure acting in opposition to said first device, motor means connected to said first and second devices and controlled by the combined action thereof in accordance with changes in compressor inlet pressure and pressure'ratio, and means connecting said motor means to said pitch varying means for automatically altering said selected torque value as a function of changes in altitude and compressor performance.

9. In regulating apparatus for a gas turbine:

propulsion powerplant including a compressor, a combustor, and a turbine arranged to drive a variable torque load device, means for automatically varying the load device to maintain the torque input thereto substantially constant at a selected value, and means including a speed responsive governor for varying the supplyof fuel sure responsive device, and means, connecting said motor means to said load varying means to reduce said selected torque value as a predee termined function of changes in the compressor pressure ratio, .and means for limiting the rate of response of said compensating means only when said compensatingmeans moves in a direction to increase said selected torque value.

10. Apparatus for controlling an internal com bustion engine and the pitch of a variable pitch propeller driven thereby, comprising a fuel flow control system including a fuel control element having a neutral position in which the fuel flow remains constant and effective upon opposite movements from said position to cause variation of the fuel flow in opposite sense, means for applying a'force' indicativeof the rate of fuel flow to said element in a fuel flow decreasing direction, and means for applying a variable fuel controlling force to said element in a fuel flow increasing direction; a propeller torque control system including a torque control element'having a neutral position in which the propeller pitch remains constant and effective upon opposite movements from said position to cause variation of the pitch in opposite senses, means for applying a force indicativeof the propeller torque to said torque control element in a pitch decreasing direction, and means for applying a variable torque controlling force to said torque control element in a pitch increasing direction; each of said controlling force applying means comprising a pair of levers having facing plane surfaces and each pivoted at one end, a bearing lying between and slidable along said surfaces, a spring acting on the free end of one of said levers and biasing it into engagement with said bearing, a connection between the free end of the other of said levers and its associated control element, and means for moving said bearing to vary the mechanism advantage between said spring andsaid associated control element; and means response to the rate of flow of air through said engine for operating both said bearing moving means.

' HUGH M. OGLE.

DONALD E. IGARR. MARTIN A. EDWARDS.

References Cited in the file of this patent Orr Dec. 28, 1948 

